Plasticized polyvinyl chloride films have been widely used as materials excellent in transparency, mechanical strength and flexibility in the fields of food packaging, medical devices and instruments and industrial materials, among others. However, plasticized polyvinyl chloride films contain a plasticizer in large amounts and therefore, when used in medical devices or instruments, pose a health problem. Further, they raise such problems as incinerator corrosion when they are burnt for disposal and the generation of dioxins. For such reasons, the demand for materials capable of serving as alternatives to plasticized polyvinyl chloride films in and outside this country. Thermoplastic polyurethane resins, for instance, are materials serving as alternatives to polyvinyl chloride. Thermoplastic polyurethane resins are excellent in such physical properties as rubber elasticity, wear resistance, chemical resistance and low temperature resistance. They are materials excellent in processability since moldings can be readily obtained from them by the conventional methods of molding/processing of thermoplastic resins (Patent Document 1).
However, thermoplastic polyurethane resins are poor in flexibility and, if their flexibility is increased by decreasing the hardness of the resins themselves, the reaction and curing in the stage of synthesis are slow, the tackiness is high and the melting point is low, hence it is difficult to produce the desired resins with great efficiency. Further, the compositions resulting from incorporation of a plasticizer raise such a problem as bleeding out. Furthermore, those resins cannot be said to be excellent in gas permeation resistance, hence cannot be said to be suited for use in the fields of food packaging and medical devices and instruments.
Patent Document 1: Japanese Kokai Publication Hei-08-27376